1. Field of the Invention
The present invention relates to a probe card and, more particularly, to a probe card having a conductive layer.
2. Background of the Invention
In processing wafers of semiconductor, to determine if dies on a wafer are good or bad, a test bench and a probe card are required to perform test of the wafer. It is provided on the probe card precise a contact mechanism to contact each die on the wafer and a conduction circuit to perform electrical test, so as to assure that the electrical properties and performance of the dies are manufactured according to the design specification.
Recently, development of high speed semiconductor devices is becoming popular. The test bench and the probe card should be operated in high frequency to accommodate the tendency. However, as a conventional probe card of a suspension arm type is applied to the high frequency test, the test result will not be very stable, quite often due to noise produced by electromagnetism interference resulting from extreme proximity of adjacent probes, such that additional test procedures are required, rendering degradation of the efficiency of production and the test.
Please refer to FIGS. 1 and 2. FIG. 1 is a three-dimensional diagram of a conventional probe card. FIG. 2 is a cross-sectional diagram of the conventional probe card. As shown in the drawings, a probe card 9 comprises a circuit board 91, a probe stand 92, a plurality of probes 93 and a plurality of conductive wires 94, in which the circuit board 91 includes an inner ring ground wire 95 and an outer ring ground wire 96, and each of the plurality of probes 93 includes a convex portion 931, an embedded portion 932 and a connection portion 933.
The probes 93 may be divided into three kinds, i.e. a high frequency signal probe, a power probe and a ground probe. Only for the high frequency signal probe and the power probe, one conductive wire 94 has to be wound surrounding the connection portion 933 of each of the plurality of probes 93 correspondingly. One end of each of the plurality of conductive wires 94 is respectively electrically connected to the inner ring ground wire 95 of the circuit board 91, and the other end of each of the plurality of conductive wire 94 is respectively electrically connected to the outer ring ground wire 96 of the circuit board 91.
Based on the principle of a current loop, due to the winding of one conductive wire 94 surrounding the connection portion 933 of each probe 93, the inner ring ground wire 95 may be extended and connected to the outer ring ground wire 96, such that the ground circuit of the probe card 9 is approaching closely to the connection portion 933 of each probe 93, rendering the loop inductance of the connection portion 933 to become smaller.
As shown in FIG. 2, the embedded portion 932 of each probe 93 is embedded into the probe stand 92. Since the conductive wire 94 only covers the connection portion 933 of each probe 93, the embedded portion 932 of each probe 93 is spaced apart a farther distance from the ground circuit, such that the loop inductance formed by the embedded portion 932 of each probe 93 is getting bigger, which will cause test signals between a chip to be tested and the probe card 9 during a test period not to transfer completely, thereby affecting accuracy of the test data.
Therefore, it is desirable to provide an improved probe card, in which the high frequency noise produced in the embedded portion 932 of each probe 93 may be removed from the internal portion of the probe stand 92, so as to mitigate and/or obviate the aforementioned problems.